public class x {
    public static void main(String[] args) {
        int x;
        double a = 0, b = 0;
        int i = 5;
        for (x = i; x >= 4; x--) {
            b = fff(x);
            a = a + b;
        }
        System.out.println(a);
    }

    private static double fff(int x) {
        double z = 0;
        if(x == 1 || x == 2 || x == 3) {
            z =  1;
        }else if(x > 3 ) {
            z =  1.0 / (x - 1) * fff(x - 1);
        }
        return z;
    }
}
